Patients requiring major cardiac or vascular surgery will be identified from routine clinical care. Most patients are routinely referred for pre-operative assessment, although local protocols vary between centres. Assesments at the pre-operative assessment clinic (PAC) may include (but not limited to) routine blood tests (full blood count, urea and electrolytes, etc.), history and examination, cardiorespiratory fitness assessment by 6 minute walk test (6MWT) or cardiopulmonary exercise testing (CPET). In some centres, patients with anaemia will receive intravenous iron at PAC or in a separate anaemia clinic.